Sustained release dosage forms have found wide usage in a variety of technology areas, such as in personal care or agricultural applications, water treatment and particularly in pharmaceutical applications. Sustained release dosage forms are designed to release a finite quantity of a compound into an aqueous environment over an extended period of time. Known sustained release pharmaceutical dosage forms contain a medicament or a vitamin whose rate of release is controlled by a polymeric matrix. Sustained release pharmaceutical dosage forms are desirable because they provide a method of delivering a long-lasting dose in a single application without overdosing. U.S. Pat. No. 4,734,285 discloses that the release of an active composition from a solid tablet can be prolonged by employing a fine particle sized hydroxypropyl methylcellulose ether composition as an excipient in the solid tablet. The particle size of the hydroxypropyl methylcellulose ether is so small that at least 90 percent by weight of the cellulose ether particles pass through a 100 mesh screen (149 micrometers mesh size), and preferably at least 97 percent by weight of the cellulose ether particles pass through a 140 mesh screen (105 micrometers mesh size) to achieve a long release profile. While such hydroxypropyl methylcellulose ether particles provide excellent release profiles to tablets, these particles of very small size are known to have poor flow properties. A poor flowability of the cellulose ether particles can lead to problems in the manufacturing of dosage forms such as tablets. Problems can include increased variability in tablet weight or tablet crushing strength from tablet-to-tablet as well as variation in the amount of active ingredient incorporated into each dosage form. Poor particle flow can also lead to consolidation of the powder bed in processing equipment, such as storage bins and tablet press feed hoppers.
The International Patent Application Publication No. WO 2008/127794 addresses the poor flowability of the hydroxypropyl methylcellulose ether disclosed in U.S. Pat. No. 4,734,285. WO 2008/127794 discloses a granular material having a mean particle diameter of 150 to 800 micrometers and an untapped bulk density of 0.1 to 0.35 g/cm3, the main component of the granular material being a cellulose derivative. The granular material is a useful excipient for sustained-release dosage forms, particularly for excipients to be used in a direct compression process, due to the good flow and the good compactibility of the granular material leading to strong, hard tablets, with small variability in tablet-to-tablet physical properties, in combination with reproducible kinetics of the sustained release of the active ingredient. Unfortunately, it has been found that the low density of the granular material may cause some problems when blending the granular material with the active ingredient. Due to the low density of the granular material, the weight of the blend of granular material and active material in the blender typically has to be reduced to avoid overfilling of the blender, which reduces the throughput through the blender. Also, formulators may need to pre-compress the blend of granular material and active ingredient to be able to fill tablet dies with the target tablet weight.
Accordingly, one object of the present invention is to find polysaccharide derivatives which are useful as an excipient in dosage forms, particularly as excipients in sustained release dosage forms, and which have an improved flowability, as compared to the cellulose ethers disclosed in U.S. Pat. No. 4,734,285. Another object of the present invention is to find polysaccharide derivatives which are useful as an excipient in dosage forms, particularly as excipients in sustained release dosage forms, and which have an improved flowability and/or an increased bulk density, as compared to the cellulose ethers disclosed in WO 2008/127794.